1) Field of the Invention
The present invention relates to the field of combating the reproduction, representation or any other illicit use of multimedia data. More specifically it relates to controlling multimedia data watermarks.
2) Description of the Related Art
With the advent of sophisticated multimedia data reproduction means, the general consumer electronics field faces the problem of illicit copies. A user should not be able to illegally copy analog or digital multimedia data. The present situation of audio CD, CD-ROM and MP3 files pirating illustrates the magnitude of this problem.
Current proposals (such as XCA, 5C, 4C, JAWS and GALAXY for example) use two basic technologies: encryption and watermarking. The invention relates more specifically to data watermarking methods and devices which have advantages associated with robustness without resorting to keys.
It is recalled that watermarking multimedia data consists in inserting an imperceptible or almost imperceptible item of information into these data. This information may relate especially to copying rights or prohibitions. Chapter 18 “A review of watermarking principles and practices” in the book “IEEE Digital Signal Processing for Multimedia Systems” written by I. J. Cox, M. Miller, J. P. Linnartz and T. Kalker, edited by K. K. Parhi and T. Nishitani in 1999, provides a description of the principles of watermarking multimedia digital data.
For a specific example of the JAWS technology developed by PHILIPS, one may refer to the article “A video watermarking system for broadcast monitoring” written by Ton Kalker, Geert Depovere, Jaap Haitsma and Maurice Maes, published in 1999 in “Proceedings SPIE, 3657 Security and Watermarking of Multimedia content”.
It transpires that security is an endless race between the ingenuity of the fraudsters and measures for combating illicit copies. Thus, watermarking techniques evolve over time without any compatibility being guaranteed between generations of watermarking. This poses two problems:                first generation multimedia data players cannot control copying of data containing only second generation watermarks;        similarly, second generation players cannot control copying of data containing only first generation watermarks.        
There is a similar problem when two different watermarking technologies are offered on the market. One player cannot analyse both kinds of watermarking.